This invention generally relates to FM-CW radar transceivers for use in motion-detector applications. More particularly, this invention relates to an improved FM-CW radar transceiver that implements both the transmitter and receiver of a conventional FM-CW transceiver into a single circuit.
It is well known that an FM-CW radar is used fundamentally to detect motion and to measure the speed of that motion. Additionally, it is well known that conventional FM-CW radars use a separate receiver and transmitter with means of multiplexing the transmitted and received signals onto a single antenna by use of either a circulator or a directional coupler.
Typically, the transmitter portion of a conventional FM-CW transceiver consists of an oscillator, power divider, and power amplifier wherein the receiver portion consists of a low-noise amplifier and a pair of "I-Q" mixers. The circulator is used to connect the receiver and transmitter to the same antenna or alternatively, because it is less expensive, a directional coupler may be used in systems where high loss is tolerable.
However, these types of conventional FM-CW transceiver systems typically require ten (10) to twenty (20) solid-state devices in association with a large number of passive components, and the use of complex DC power supplies. Additionally, when conventional FM-CW transceiver systems are implemented in monolithic form, they require at least ten times the chip area than similar RF circuits, and since large chips have low yield, the cost may be quite prohibitive for large scale commercial applications.
Therefore, there is a need for an FM-CW transceiver system having a transmitter and receiver as a single unit as opposed to a conventional system having a separate transmitter and receiver. Further, there is a need to provide an FM-CW transceiver system having a simplified circuit using only two solid-state devices, a few passive devices, and does not require the use of either a circulator or coupler. The subject invention herein solves all of these problems in a new and unique manner which has not been part of the art previously.